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KA-NON has left a new comment on your post "Pedantic...Maybe. Precise...Hardly":


@12:17 - My understanding is that, upon scrutiny, Wikipedia is roughly as accurate as the best collections of encylopedias have ever been (i.e. Britannica). They've studied this, apparently.
see the link below

http://news.bbc.co.uk/2/hi/technology/4530930.stm

Having said that, the real point to be made is that the specific link that Cllr. Pirri presents does not effectively challenge Evelyn's point. It merely changes the temperature of it.

Below is a Wikipedia excerpt, on the solubility of salt in water. FYI NaCl is the chemical formula for Salt.

"When dissolved in water, the sodium chloride framework disintegrates as the Na+ and Cl− ions become surrounded by the polar water molecules. These solutions consist of metal aquo complex with the formula [Na(H2O)8]+, with the Na-O distance of 250 pm. The chloride ions are also strongly solvated, each being surrounded by an average of 6 molecules of water.[4] Solutions of sodium chloride have very different properties from pure water. The freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is near 108.7 °C (227.7 °F).[5] From cold solutions, salt crystallises as the dihydrate NaCl·2H2O."

The link for the above
this excerpt is below.

http://en.wikipedia.org/wiki/Sodium_chloride

So, at a temperature ABOVE -21.12 celcius, the salt melts the snow and is then dissolved in the resulting water, which would have otherwise been frozen at 0 degrees. That is indeed the whole point - melt the snow and ice so that tires can grip the road underneath. The snow/salt water solution then flows where gravity takes it, meaning, the salt does not take up residence in the snow.

At temperatures BELOW -21.12 degrees celcius, I believe that the salt would remain among the snow and ice. So on those days, the snow that is picked up would have salt in its midst.

This link

http://www.worldweatheronline.com/Newmarket-weather-averages/Ontario/CA.aspx

provides the average daily temperatures throughout the year for Newmarket (closest to Aurora on the site). The coldest months, on average, are January and February, with an average daily temperature of -9 degrees celcius. Now of course, we all know that there are some cold days that are below -21 degrees - but not many. Less than a handful each year, I would bet. Remember, we are NOT talking wind-chill - just temp.

So, notwithstanding Cllr. Pirri's freezing point depression point, for all practical purposes, it seems that Evelyn's theory is correct. That is, the salt melts the snow and ice (yay - fewer traffic accidents!) and the resultant liquid solution goes where Newton knew it would.

One more thing. In places that DO have sustained temperatures below -21.12 celcius, they don't use salt on the roads. They use dirt as a grit to provide traction ON TOP OF the ice. Now you know why.


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Posted by KA-NON to Our Town and Its Business at 13 August 2014 13:04